What are the shifts like at various engine speeds?

Perform full throttle or close to full throttle up and downshifts and see what the gearbox does. If there is flaring then you can adjust the modulator pressure.

If the upshifts are soft and the downshifts hard then it's not the pressure and it really needs someone who can diagnose these boxes.

At that milage a rebuild wouldn't be out of the question.

Matt.